Smoked 2nd esc in a row...

I suggest double checking the motor, and soldering it up PROPERLY to test it. Soldering it up half assed is not a great troubleshooting technique. If you experience severe cogging on the mamba max (what firmware- that makes a difference). If I remember right, the X11 is rebuildable, so you should be able to open the motor up and check the windings where the motor screws may short out the wire. A shorted motor would explain a FET failure from over current or something.

I've owned brushed LRP ESCs, and I've had one be DOA (new-in-box too!). They replaced it with a second one, and that one was dead as well. Third time was the charm.